Checking someone else's arithmetic: a worked example thread posts 61–79
This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
I read post #62 twice before replying, because I had assumed the opposite.
Preservative effectiveness is tested against a defined microbial challenge under defined conditions. It is not a licence to treat an entered vial as sterile indefinitely, and no supplier claims otherwise.
Two people can read the same figure differently here and both be reasonable.
Sensible. I would want the same detail before I acted on it either.
Do not shake. Swirl, or leave it. Vigorous agitation introduces air and shear, and neither helps a peptide go into solution any faster than patience does.
Post #65 is right about the mechanism and I think understates the practical bit.
Preservative effectiveness is tested against a defined microbial challenge under defined conditions. It is not a licence to treat an entered vial as sterile indefinitely, and no supplier claims otherwise.
Filing this under things that are true until someone shows me otherwise.
Where I part company with post #65, and it is a narrow parting.
Do not shake. Swirl, or leave it. Vigorous agitation introduces air and shear, and neither helps a peptide go into solution any faster than patience does.
If anyone can point at the primary source I would be grateful.
Preservative effectiveness is tested against a defined microbial challenge under defined conditions. It is not a licence to treat an entered vial as sterile indefinitely, and no supplier claims otherwise.
Do not shake. Swirl, or leave it. Vigorous agitation introduces air and shear, and neither helps a peptide go into solution any faster than patience does.
It is one reading of the data and not the only reasonable one.
On post #70 — agreed on the reasoning, with one qualification.
Preservative effectiveness is tested against a defined microbial challenge under defined conditions. It is not a licence to treat an entered vial as sterile indefinitely, and no supplier claims otherwise.
Post #72 is right about the mechanism and I think understates the practical bit.
Worked example, since the arithmetic is the whole question. Five milligrams into one millilitre is 5 mg/mL. A 0.25 mg dose is 0.05 mL, which is five units on a U-100 syringe. Check that against your own numbers rather than taking mine.
A 10 mg vial reconstituted three different ways: 1 mL diluent gives 10 mg/mL, 2 mL gives 5 mg/mL, 4 mL gives roughly 2.5 mg/mL. The arithmetic is the same; the concentration determines which syringe graduations are legible.
The interesting part of this is the exception, and I do not understand the exception.
Preservative effectiveness is tested against a defined microbial challenge under defined conditions. It is not a licence to treat an entered vial as sterile indefinitely, and no supplier claims otherwise.
I have kept the units in throughout, for the obvious reason.
Taking post #76 at face value and following it one step further.
Preservative effectiveness is tested against a defined microbial challenge under defined conditions. It is not a licence to treat an entered vial as sterile indefinitely, and no supplier claims otherwise.
The evidence for this is thinner than the way I have phrased it suggests.
This topic was referenced in
- Foaming during reconstitution and whether it matters — the long versionPractice › Reconstitution · 117 replies
- Reconstituting a multi-strength kit without mixing yourself up — what changed sincePractice › Reconstitution · 46 replies
Suggested topics
| Topic | Participants | Replies | Views | Activity |
|---|---|---|---|---|
|
A 5 mg vial and a 0.25 mg dose: the arithmetic in full
A 5 mg vial and a 0.25 mg dose: the arithmetic in full Writing it up because I had to work it out twice and would rather nobody else did. 5 mg vial: setting out the arithmetic in full, because I have had to…
|
+124 | 141 | 16k | 2d |
|
[2026 update] How much of the diluent volume the powder itself displaces
The question in the title: How much of the diluent volume the powder itself displaces I will give what I have already checked below so nobody repeats it. Writing this out with the numbers in it, because…
|
+89 | 100 | 3.2k | 8mo |
|
Foaming during reconstitution and whether it matters
Posting this under the heading it deserves: Foaming during reconstitution and whether it matters Everything below is what sits behind that. A follow-up question about foaming during reconstitution that I did…
|
+19 | 24 | 466 | 11mo |
|
[2026 update] A vial that will not fully dissolve: what to check and in what order
Posting this under the heading it deserves: A vial that will not fully dissolve: what to check and in what order Everything below is what sits behind that. Practical question with the units stated, because I…
|
+114 | 128 | 20k | 1mo |
|
The decimal-point error, and the habit that catches it
The decimal-point error, and the habit that catches it Writing it up because I had to work it out twice and would rather nobody else did. An honest uncertainty about decimal-point error rather than a…
|
+110 | 121 | 10k | 7mo |
Related topics — sharing the tags reconstitution, syringe units, concentration maths
| Topic | Participants | Replies | Views | Activity |
|---|---|---|---|---|
|
Second pass at: Multiplicity when you track fifteen variables
Posting this under the heading it deserves: Second pass at: Multiplicity when you track fifteen variables Everything below is what sits behind that. Two things I would like separated before anyone answers on…
|
2 | 12k | 18mo | |
|
[2026 update] How much of the diluent volume the powder itself displaces
The question in the title: How much of the diluent volume the powder itself displaces I will give what I have already checked below so nobody repeats it. Writing this out with the numbers in it, because…
|
+89 | 100 | 3.2k | 8mo |
|
Coming back to: Checking someone else's arithmetic: a worked example thread
Posting this under the heading it deserves: Checking someone else's arithmetic: a worked example thread Everything below is what sits behind that. Practical question with the units stated, because I have seen…
|
+13 | 17 | 293 | 11mo |
|
Follow-up: Bug report: the reconstitution calculator and a rounding edge case
On the subject in the title: Bug report: the reconstitution calculator and a rounding edge case Working notes rather than a conclusion. Posting the calculation with the inputs, so that somebody can disagree…
|
+58 | 63 | 24k | 5mo |
|
A calculator that gives a right answer to the wrong question — does this still hold?
A calculator that gives a right answer to the wrong question — does this still hold? I have a specific reason for asking rather than idle curiosity, and the context is below. Posting the calculation with the…
|
+23 | 27 | 62k | 8mo |